Underfloor duct system



July 13 1926.

H. S. WALKER UNDERFLOOR DUCT SYSTEM Filed Oct. 19 1925 2 Sheets-Sheet 1 Fig].

ATTORNEYS H. S. WALKER UNDERFLOOR DUCT SYSTEM July 13 1926.

2 Sheets-Sheet 2 Filed Oct. 19, 1925 ATTORNEYS Patented July 13, 1926.

UNITED STATES PATENT v orFrcE.

HERVEY S. WALKER, F ARDMORE, PENNSYLVANIA.

UNDERFLOOR DUCT SYSTEM.

Application filed October 19', 1925. Serial No. 63,355.

This invention relatesfto systems of elec-.

'service'on each floor of thebuilding. High' teiiionenergy for lightingand small power devices, such as fans, andthelike, must be available on account of the numerous desks disposed within a given area, and in addition telephone wiring is necessary, and also wiring for low tension signal systems, such as buzzers, annunciators, and the like. The conductors for these different services must be concealed and protected and in modern practice the conductors are led to .the different parts of the floor in ducts built into the floor during the course of construction of the latter. Such systems are commonly referred to as under-floor Wiring systems,

In steel frame structures, such as office buildings, the same general method of making floors has been followed for the past thirty years. While there are'apparent differences in construction, actually these dif-v ferenc'es are of a minor character The floor consists essentially ofan arch or slab cast or built on suitable forms, this slab having a rough upper surface which may be finished in several different ways. At one time it was the general practice to place wood sleepers on the slab and then lay wood flooring over the sleepers, the spaces between the sleepers providing run-ways for'the conductors or ducts of the wiring system. Sometimes the sleepers were channeled for the purpose. More recently the use of wood has been avoided, and the finished surface of the floor has been formed of a finishing layer of cement mortar, over which linoleum or some other similar product is almost invariably laid to provide the necessary resilience. In this latter construction a cinder t0 fill is usually interposed between the slab and the finishing layer, the fill being a cin-r der concrete with a small proportion of'ccment. When marble is used as a finishing layer, a suitablebed of concrete-isflaid on the slab and the marble placed in position on this bed. i In constructions .in which the floor includes a finishing layer of concreteto be, 7 covered with linoleum in the usual way, the

ducts are placed in position 'duringthe con-.60

struction of the floor, and may belaid in; the finishing layer of concrete when the" latter is being poured, either t'o'lie' flush with the surface of the latter, orelse. placed somewhat more deeply beneath thefloon oo surface, usually being supported "on the floor slab and embedded in the fill, A typical,

system of the type referred to is shown; the Alexander Patent No. 858,8d6, i ssued i.

July 2, 1907. 1

The laying of the ducts flush with' t-he floor surface provides greater accessibility, but is objectionable because it is diflicult and expensive to secure watertight connections with this arrangement. The present tendency in building construction is therefore to embed the ducts a substantial distance beneath the top surface, and the duct systems are placed within the floor structure at that stage of the construction when the 'slabflisflo completed and before the cinderfill is inpo'; sition. The ducts or conduits are support 1 ed on the slab and are completely concealed, being covered by a portion of the fill and by the finishing layer. With suchan arrange ment, whenever a connection is to be made, the linoleum and finished floor surface must I be cut through at a point near the device to be supplied with current, a quantity of fill ing material removed to exposethe duct, the latter opened by a suitable operation. such as drilling. and a fittting similar to a bushing inserted in the opening so made. This fitting extends to the floor surface and with the present practice a standpipe is always placed in the end of the fitting through which connections are made. With this type of system, it will be apparent that the making of a connection to a conductor in the duct necessitates cutting the floor surface after'the latter is finished, and the operation is completed by patching the surface. Such work is not only laborious and expensive, but carelessness on the part of the workman may result in the floor being rough or uneven around the point where the connection was made. Furthermore, such connections cannot be made ordinarilyiv until just before the space is turned over to the tenants and frequently the work has to be done While the otfice equipment is being moved into position. Thus the Work is nearly always carried on at a time when little opportunity is afforded for it, and it must be hurried to completion as rapidly as possible.

The present system has been devised for the purpose of obviating the difiiculties inherent in the system above described, and is intended to take advantage of the features of modern building construction which af ford a convenient method of concealing the duct system, while at the same time avoiding the ditticulties involved in cutting through the floor whenever a connection is to be made. In the present system the conduits or ducts which are adapted to receive a plurality of conductors, are placed beneath the fioor level and are preferably supported a short distance beneath the finished fioor surface. The system is made up of ducts to carry main circuit conductors and other branch circuit conductors are housed. The

number of ducts in the system depends on the number of different kinds of electrical service to be provided, and each of these ducts contains a plurality of inserts placed in it in definite spaced relation prior to its installation. These inserts are of cheap construction and are temporarily closed by caps.

The inserts are spaced relatively closely together in the duct, and the number of inserts in a given length of duct is such that more inserts are provided than would be required by normal demand. In the installation of the duct, it is placed in position so that the tops of the inserts lie substantially in the floor level and portions of the cap may be visible in the floor though ordinarily concealed by the linoleum. A large number of these inserts are placed in each duct. and the distance between adjacent inserts is small, so that regardless of the position of the devices which are to be supplied with current, there will always be an insert fairly close at hand, so that the wires extending from the insert to-the device will not be objectionably long. Under ordinary circumstances there will be a number of the inserts which are not used, but these inserts are always available for use and as the inserts are does not add materially to the cost of the system and the convenience afforded by the presence of the inserts is highly desirable.

After the completion of the floor structure, whenever a device is to be connected to a conductor in a duct, an opening is made in the linoleum, the cap in the insert is pried loose and a bushing is placed in position in the end of the insert which is adapted to receive the standard type of standpipe. The conductors are then connected to the device through the insert and the standpipe in the usual way.

By the use of a duct of the type described, which has a plurality of inserts mounted in it prior to its installation in the floor, the necessity of cutting through the concrete floor, removing the filling material, drilling or otherwise cutting into the duct, installing the fitting, and thereafter patching the floor to close the opening made, is entirely avoided. The insert is opened simply by prying loose the cap placed in the end of it, and consequently making a connection is a simple matter which can be done quickly and which involves little expenditure for material or labor. The inserts preset in the duct are of cheap construction, and are not comparable in cost with the expensive brass fittings employed with the system heretofore use, so that a great many of these inserts may be inserted in the duct withoutmdding materially to the cost of the latter, and the eventual saving resulting from the lower labor cost for making connections, and also from the elimination of fittings which must be threaded into the duct in order to he sat isfactorily mounted, is pronounced. The presence of inserts in the duct which are not used is not objectionable, because these in serts do not extend above the floor level. At the same time, since the inserts are always in position connections may be quickly and conveniently made at any point in the system.

The present invention not only includes a method of installing a wiring system pres= ently to be described, but also comprises certain new parts, such as the novel type of duct, new floor boxes which have been devised for use in the system, and other parts which will be pointed out hereafter.

For a better understanding of the invention. reference will be made to the accompanying drawings, in which,

Fig. 1 is a plan view of a portion of a duct system constructed in accordance with this invention,

Fig. 2 is a cross sectional view through a single duct, and one of the inserts,

Fig. 3 is a view similar to Fig. 2, but showing a standpipe inserted in an insert,

Fig. 4 is a View similar to Fig. 2, but showing a different closure member used as a guide,

Fig.4 is a plan view of a section of three.

ducts showing a supporting member employed with them, D

Fig. 6 is a side View partly in section, showing the parts illustrated "in Fig. 4.,

Fig. 7 is a top plan view partly in section, showing a novel type of-cross-over box,

Fi 8 is a sectional .view of the boxon the hue 88 of Fig. 7,:

Fig. 9 is a sectional view on the line 9-9 of Fig. 7, and

Figs. IO-and 11 are vertical sectional views of two different types of boxes which may be used in place of the box shown in Fig. 7, but to serve other purposes. 7

Referrin now to the drawings, and particularly Fig. 1,, thesystem is there illustrated-as including jdujcts for three different sets .of condu'ctoraand these ducts are laid in a network throughout the building. Or

dinarily they consist of ducts for main circuit conductors, generally designated 11, and ducts for branch circuit conductors, generally designated 12. The number of ducts employed will of course depend on the different types of service to be provided. The system illustrated involves the use of ducts arranged in groups of three, and the ducts of the circuit branch conductors extend at right angles to the main line ducts. Where the two sets of ducts meet, floor boxes 13 are provided which serve as centers of distribution. These boxes may be of different lii'nds, and will presently be described in detail. In some cases the two sets of ducts lie in different planes'in the floor, but it is in many instances preferable that the ducts for both main and branch circuits should lie in the same plane; and such an arrangement maybe utilized by makingns of a novel type of box illustrated in Figs. 7 and 8.

The ducts preferably employed in the present system, as at 14, are square in cross section, and are made of comparatively thin steel, as, for example 14 gauge. These ducts are used in lengths such as 10 feet, and are connected together in any desired length by means of sleeve cou lings 15, which fit over the ends of'a pair o ducts in alignment, and are secured in place by set screws. Inone of the flat surfaces of the duct are mounted a plurality of tubular inserts 16, preferably in a permanent manner, and for ordinary purposes it will bedesirable to have these nserts placed at approximately 30 spacing.

hese inserts are made of a short length of thin metallic tube, and are inserted inopenings in the duct, as shown in Fig. 2. They may be held permanently in position by means of a crimped flange 17 which overlies the outer face of the duct around the opening and an inner outwardly turned edge 18 which overlies the inner face of the duct around ;the opening. The ends of the inserts are normally closed by means'of a cap 19 which has a central depressed portion entering and closely fitting theinside of the insert and a rim 20 .-which fitsf over the edge of the latter.

In the installation of the ducts, they are supported onthe rough floor slab 21, in such.

position that the tops of the inserts will lie substantially flush with the level of the finished floor, as shown in Fig. 2. It is preferable to support the ducts at a slight distance above the floor slab so that variations tween adjacent seats, screws '24 are provided having washers 25 overlying the edges of adjacent ducts and so arranged that by tightening the screw the ducts will be held firmly in the seats. The supports 22 rest directly on the floor slab, and a higher or lower support will be provided as the floor structure may require. In some instances it may be desirable to form the supports 22 with openings in the legs'through which a screw 22may be inserted to extend a slight distance into the concrete. This provides an additional anchorage for the supports. -Also, the supports, as will be seen from 5, hold the ducts in spaced relation so that the cement mortar or cinder fill, as the case may thus-hold them firmly in position as well as entirely encasing them.

Asipreviously explained, the tops of the inserts with the caps 19 are intended to lie substantially at the floor level, so that the flanges 20 of the caps will lie flush with the floor surface and be exposed. lVhen cement is used for the finishing layer, however, a certain amount of shrinkage occurs and if the duct system were to be installed so that the caps of the inserts lie exactly in the floor level, it would be necessary to mix the cement with extreme care in order to prevent the projection of the cap above the surface. In order to avoid this it is customary to set the ducts so that the caps he a slight distance beneath the floor surface, but the caps are covered only by a very thin layer of the finishing material and no difliculty is experienced in getting atthem by chipping away this material. This, it will be understood, is quite a diflerent operation from cutting through the entire finished surface, and removing material so as to expose the duct, as is necessary in the system heretoforefollowed' Whenever a connection is to be made.

be, can enter between the ducts and By installing branch line ducts at the desired intervals, this system provides a great many inserts through whichconnection may be made to the conductors within the ducts, and the inserts are placed so near'together that no considerable length of wire need run along the floor from the insert to the device which is to be supplied with current. When the'installation is in place, and a connection is to be made, the workman can readily locate the nearest insert to the device to be connected, since the caps of the inserts are exposed in the floor. In order to assist the workman in locating the inserts in the duct, especially when the latter is installed in such manner that the caps of the inserts are not visible at the floor level, due to the use of linoleum, a brass cap 26 is placed in the inserts nearest the floor box, this cap, as shown in Fig. 4, being solid and of asuflicient thickness so that its face will be exposed through the floor and flush with the linoleum.. It is placed in position before the floor is finished and by measuring along the duct in alignment with the box and the cap, the workman can locate the nearest insert to any point in the floor, since the inserts are evenly and definitely spaced from the first insert nearest the box.

Whenever a connection is to be made for supplyin current, the insert nearest the device to e operated or the desk, as the case may be, is opened by the removal of the cap 19, and then an expansible bushing 27, usually of brass, is placed in the insert. This bushing is slit, as indicated at 28, and is internally threaded. It has a flange 29, which is intended to overlie the floor surface at the point at which the insert has been exposed. Into this bushing is threaded a standpipe 30 of the usual type and in inserting the standpipe in the bushing the latter is expanded-so that it grips the insert tightly. The standpipe used will depend on the type of conductor which is to be connected. That illustrated in Fig. 3 is of the high tension type, and carries a receptacle 31 at its upper end into which a plug may be inserte With the new system it will be seen that the cost of making a connect-ion'is quite small because little labor is involved and only a single bushing is necessary. In the system as heretofore used the labor involved in making connection is much higher. because it is necessary to cut through the floor, to clear awaythe material to ex ose the duct, then drill an opening in the not, insert a fitting in the opening which extends to the floor level, and patch the floor around this fittin The cost for material with the previous uct s stem is also higher because the fitting whic is inserted in the duct and extends from the latter to the floor surface, is much more expensive than the bushing required with the present system. The

standpipe used in each case is substantially the same. Consequently, by using the present system in which the cost of making an insert is so small, it is possible Without adding to the final cost of the installation, to provide a large number of inserts in the duct before it is placed in the floor, and this permits connections to be made quickly and at a low cost. Not only is the saving involved in the use of the new system quite pronounced, but it is more'convenient to use.

As shown in Fig. 1, at the places where the conduits or ducts extending transversely of each other meet, boxes 13 are employed which may be of several different types. In Figs. 7, 8, and 9 there is illustrated a type of floor box constructed to permit the installation of the ducts all in a single plane.

This box is made of upper and lower sections 32 and 33. The box is made of metal and may conveniently be cast iron.

channels 36. The box illustrated is for use in a three duct system, and three such channels are provided. The upper section 32 is secured to the lower section by screws 37 entering lugs 38 formed integrally with the lower section, and at either end the lower section has extensions 39 which are inclined upwardly and provided at their outer ends with supporting lugs 40, the lower ends of which lie in the same plane as the bottom of the lower section. The extensions are formed with channels similar to the channels 36.

The upper section of the box COIiSlStS of a body portion which is octagonal and provided with a cover plate 41, which is held in position by screws 42. The cover has a central opening 43 provided with spaced upstanding flanges 44 and 45, in which is to be received the flange 46 of a cover 47. The latter is to lie flush with the floor and the flange has adjustment screws 48 which .enter the space between the flanges 44 and 45 on the cover plate. By properly setting these adjustment screws the cover may be raised or lowered slightly.

The lower end of the upper section is closed by a bottom plate 49 which has arched portions 50 extending between the upstanding walls 35 of the lower section and with these walls formin an arched top for the passages 36. Exten ing transversely of these arched portions are walls 51, which divide the upper section into passages 52, extending transversely of the passages in the lower section. In each of'the passages defined by the arched portions 50 of the bottom plate and the upstanding. walls 51, the bottom late is cut away as at 53 to form an openmg through which 3 96 maybe had from a passage in the upper portion of:-the box to a passagein the lower portion. There are ductors entering through the duct 55. The

conductors in duct 56 may .be-connected to the conductors in duct 57, and those in duct 58 to those in duct 59. Theco'ver plate is also provided with downwardly extending walls 60 which lie in contact with the .walls 51 within the box.

Opposite end walls 61. and 62 of the upper section of the box have square openings in which the ends of the'ducts55,57, and 59 may be received. These openings are channeled as at 63, so that packing ma be inserted to enclose the ends of t e ducts, and the cover plate 41' is providedwitlr set screws 64 by' which-'tlie ends of the ductsmay be firmly placed 'in'posi'tion. From the upper box section there Iareiextensions i65' at either end which cooperate with- "the' extensions 39' to. form tubular passa es through which the conductors maybe ed through the box from ducts 54, 56, and 58. These tubular passages are inclined downwardly at an angle, and have end openings 66 into which the ends of the ducts are re ceived. These openings are placed in the same plane as the openings in the wall of the upper box section, into. which ducts 55, 57, and 59 enter so that all the ducts, both parallel and transverse, lie in the same plane. The upper ends of; the extensions 65 are cut away to form an opening throughwhich the ducts may be placed in the openings 66. The cut away portion of the extensions is covered by a plate. 67, held in place by screws 68' and the openings 66 are channeled as indicated at- 69 for the insertion of packing. With this arrangement the box may be permanently set in position and the ducts may then be inserted thereafter. The plates 67 not only permitthe ducts to be placed properly in position after the box is installed,.but also permit the ends of the ducts after they are placed, to be inspected so that any roughnesses which might in'ure the conductors may be removed. by which the ends of the ducts are firmly anchored in place.

In the corners the upper box section is providedwith openings71 into which round conduit maybe threaded. Such conduit will run off at a 45 angle to the ducts, and may be used for feed wires. or. for other purposes. The ducts, the ends of whlch are shown in position-in the box, are square ducts, but

round conduit maybe employed by making use of anadapter which is a square plateintended to be placed in the openings in the box and provided with threaded openhe plates 67 carry set screws 70,

standingwalls 79. The .box 1s supported ing in the center into which'the round conduit may be inserted. The box shown in Figs. 7, 8, and 9- is of the cross-over splice type, that is, the ducts used are all of the same type,and the box contains openings through which connection may be made between .the conductors running through the ducts extending in one direction and those extendingtransversely.

In Fig; 10 there is shown in section a dif; ferent kind of box, which is of the junction tpe. Round conduit 7 2 is threaded into t e op osite sides of the box while alternate si es have square openings 7 3 in which the endsof square ducts may be received. This box is for use in a system in which the ant planes, the round conduit lying in a lower plane than the duct connected in the type of box the lower section contains passages for the conductors extending through both conduits and ducts. The upper section which rests above and is secured to the lower section by bolts 75, has a central opening 76, closed by a cover plate not shown. In other respects the construction of the box is similar to that above described.

In-Fig. 11 there is shown another type of box in which the ducts leading from the box lie in a single level, but inthis box separate channels for the conductors are not provided. The conductors extending across the box between one set of ducts lie in channels which open directly into other channels reon feet 80 and is channeled as at 81 in its upper edge to receive a cover plate similar to that previously described.

The boxes above described purposes, as set forth, and these boxes the new form of ducts provide the parts for a system which may be readily installed and serve different main and'branch line conduits lie in difl'erlit which has numerous advanta es over the s'ystems as heretofore .em loye The present system may be installe at a low expense for labor .charges because the boxes are constructed so that, they may be given a ennasaid ducts havin nent setting on the slab before the duct is connected to them. Also, by the use of preset inserts of appropriate height in the ducts, the laying of the floor is greatly simplified because the tops of the inserts provide guides for the workman putting down the finished floor surface, and as these inserts are a comparatively short distance apart, it is quite simple for the workman to produce a level floor surface. In such a system the building owner is assured of a large number of openings in the duct which can be made use of at any time at a low expense and the convenience of the system and 1ts cheapness in use, due to the ease with which connections may be made in it at any time, will be apparent.

I claim 1. A concealed wiring system for concrete building including a wiring duct wholly within the floor structure at a substantial distance beneath the finished floor surface, said duct having a wall provided with a plurality of parallel tubular inserts relatively closely spaced at predetermined regulated uniform intervals prior to the installation of the duct in the floor, embedded in the floor structure with the insert outlets opening throu h the floor surface.

2. building including wiring ducts wholly within the floor structure at a substantial distance beneath the finished floor surface, a wall provided with a plurality of para el tubular inserts relative- 1y closely spaced at predetermined regulated uniform intervals in the said wall rior to the installation of the ducts in t e floor structure, the said ducts being embedded in the floor structure with the insert outlets opening through the floor surface, and boxes in the floor structure with which the ducts communicate, these boxes having outlets floor structure at a substantial distance from concealed wiring system for concrete Within the floor structure at a substantial.

distance beneath the finished floor surface, said duct having a wall provided with a plurality of parallel tubular inserts relatively closely spaced at predetermined regulated uniform intervals prior to the installation of the duct in the floor structure, the said duct being embedded in the floor structure with the outlets of the inserts lying substantially in the level of the floor surface, and caps mounted removably in the ends of the inserts.

5. A concealed wiring system for concrete building, including a wiring duct wholly within the floor structure at a substantial distance beneath the finished floor surface, said duct having a wall provided with a plurality of vertical tubular inserts of uniform internal diameter, the said duct being embedded in the floor structure with the outlets of the inserts lying substantially in the level of the floor surface, and standpipes mounted in the ends of selected inserts and extending above the floor surface, the remaining inserts being closed by caps and the caps and standpipes being interchangeable.

6. A duct for use in a concealed wiring system and adapted to be disposed wholly within the floor structure at a substantial distance beneath the finished floor surface, which comprises'a metal tube provided with a plurality of parallel tubular inserts mounted in the wall of the tube in a row at predetermined uniform relatively short intervals and providing outlets opening through the floor surface.

7. A duct for use in a concealed wiring system and adapted to be disposed wholly within the floor structure at a substantial distance beneath the finishedfloor surface, which comprises a metal tube with a plurality of apertures in a row in'its wall at predetermined regulated uniform relatively short intervals, and tubular inserts mounted-perma-nently in the a ertures and lying parallel to one another, these inserts having outlets through which access to the interior of the duct may be had through the finished floor surface.

8. In a concealed wirin system, a wiring duct wholly within the oor structure at a substantial distance beneath the finished floor surface, said duct having a'wall provided with a tubular insert, the insert outlet opening through the floor surface, an expansible bushing mounted in the insert and terminating above the floor surface, and a stand-pipe having one end received in the bushing and forcing the latter into tight engagement with the inner surface of the insert.

9. In a concealed wiring system,'a wiring duct wholl within the floor structure at a substantial istance beneath the finished floor surface, said duct having a walhprosurface and e stand-pipe having one end vlded with a tubular insert, the insert outreceived 1n 'the bushing and forcing the let opening through the floor surface, an exlatter into tight engagement with the inner 1 pansible bushing mounted in the insert and surface of the insert.

6 terminating above the floor surface, this In testimony whereof I affix my signabnshing having a flange overlying the end ture. of the insert and resting on the finished floor HERVEY S. WALKER, 

